Enhanced molecular selectivity and plasticization resistance in ring-opened Tröger's base polymer membranes

As a new class of membrane materials, Tröger's base (TB) polymers suffer from CO 2 -induced plasticization , which leads to a loss in their gas separation selectivity . To address this challenge, we describe a new approach for enhancing their plasticization resistance by ring-opening a TB polymer to establish hydrogen bonds between polymer chains. The ring-opened membranes, called TB-OR, exhibit H 2 /CO 2 and H 2 /CH 4 selectivities of 5.1 and 186.7, respectively. High-pressure CO 2 feed measurements reveal that the TB-OR membranes possess better plasticization resistance than untreated TB polymers. The increased plasticization resistance is likely due to hydrogen bonds formed between –N-H groups and N atoms in TB-OR polymers, which reduce the polymer chain mobility and CO 2 -induced swelling of polymers. The design principles open a new route for making molecularly-selective membranes with significantly enhanced CO 2 plasticization resistance that are potentially useful for CO 2 separation and hydrogen purification.